<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>02-百度换肤</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    body {
      background: url(images/1.jpg) no-repeat center top;
    }

    li {
      list-style: none;
    }

    .baidu {
      overflow: hidden;
      margin: 100px auto;
      background-color: #fff;
      width: 410px;
      padding-top: 3px;
    }

    .baidu li {
      float: left;
      margin: 0 1px;
      cursor: pointer;
    }

    .baidu img {
      width: 100px;
    }
  </style>
</head>

<body>
  <ul class="baidu">
    <li><img src="images/1.jpg"></li>
    <li><img src="images/2.jpg"></li>
    <li><img src="images/3.jpg"></li>
    <li><img src="images/4.jpg"></li>
  </ul>
  <script>
    // 1. 获取所有img元素
    var imgs = document.getElementsByTagName('img');

    // 2. 注册事件 处理程序
    for (var i = 0; i < imgs.length; i++) {
      console.log(imgs[i]);
      imgs[i].onclick = function () {
        document.body.style.background = 'url(' + this.src + ')';
      }
    }
  </script>
</body>

</html>